As you may know, most of the phones’ coming of late support a technology called USB OTG (On The Go), where users can simply connect an external USB drive to their phone using the OTG cable and access files (either transfer them or directly play the media on the phone).
The Samsung Galaxy S2 is one such phone that supports USB OTG. You can get the cable from any retailed for about $4 or Rs.200 (search in eBay for Galaxy S2 USB OTG). You can connect any of your USB devices to your Galaxy S2 and transfer files between then or directly play media such as Videos or music from the USB drive on your phone.
The files present in the USB device can be accessed using ‘My Files’ app. Go to folder called ‘usbStorage’ to see the list of files. To transfer files, you can long press and then use the ‘Move’ feature.
Apart from being able to connect USB devices, you may also connect a keyboard using the OTG Cable.
Note: You may also connect external HDD but most of them won’t work (even if they are small and doesn’t require AC power). For example, the Seagate GoFlex Ultra-Portable drive is small and doesn’t require external power; but when connected to Galaxy S2, the phone shows up a warning ‘High-Power USB device connected. Cannot access to this device’. The warning is self-explanatory. If you didn’t understand, it is telling you that the device you connected needs a lot more power than what your phone can provide it with to make it work.
Also see: Galaxy S2 security (track, remote wipe)